Due to advances in research and development for magnetic storage media represented by recent magnetic hard disks, magnetic storage media with an array of nanomagnets having a thickness of 25 nm or less will soon be available. However, analysis tools for practically evaluating such media are still under investigation. Accordingly, it is currently difficult to achieve thorough evaluation.
Indeed, even in the prior art, while various magnetic properties can be evaluated by using scanning electron microscopy or tunneling microscopy that uses spin-polarized electrons, observations with these analytical devices cannot be achieved unless the sample surface is extremely clean. In particular, one must process the surface in an ultra-high vacuum device and prepare a detection device for special electric signals. Thus, these analytical devices have not been widely used in the research and development of magnetic recording.
Meanwhile, the magnetic force microscope (MFM) is known as one of the scanning probe microscopes that measure shapes and physical properties of micro areas through the detection of various physical quantities between the probe and a sample. The scanning magnetic force microscope detects magnetic forces between the probe and the sample (typically, a ferromagnetic body). The detection principle is based on the magnetic field leakage from the sample, and, thus, quantitative evaluation of the magnetic properties of the sample is difficult. However, due to its insensitivity to the condition of the sample surface, the microscope has great practical advantage in that it requires neither a specific environment nor specific processing of the sample surface to perform observation.
Due to such characteristic features of the scanning magnetic force microscope, there has been an expectation that the microscope would be applicable to the research and development of magnetic media. However, the resolution achieved by commercially available devices generally ranges only about 50 to 100 nm, and even current state-of-art devices have achieved only a resolution of about 20 to 30 nm. Thus, it is currently difficult to evaluate magnetic storage media in the research and development of next generation hard disk, nonvolatile random-access memory, and the like.
To improve the resolution of the scanning probe microscope, it has been suggested that the probe tip be acuminated. Conventional techniques known for preparing such probe tips that can be used for testing magnetic properties include: (1) forming a cylindrical process of tungsten or diamond-like carbon (DLC) using focused ion beam (FIB) on the platform shaped as a base; and (2) attaching a carbon nanotube onto the platform shaped as a base and coated it along its bottom circumference using focused ion beam (see, for example, Japanese Patent Application Kokai Publication No. (JP-A) 2003-240700 (unexamined, published Japanese patent application)).
Alternatively, there exists a technology established by the present inventors, which achieves high resolution applicable to 1100-kFCI media by employing a cantilever for a magnetic force microscope (MFM) that comprises a carbon nanotube (a diameter up to about 11 nm) isotropically coated with a ferromagnetic CoFe thin film using spattering device (the diameter of the coated carbon nanotube tip is about 40 nm) (see, for example, Manago, T. et al., Extended Abstracts of the 2004 International Conference on Solid State Devices and Materials, pp. 638-639 (Sep. 15, 2004); and Kuramochi H et al., Nanotechnology, Vol. 16, pp. 24-27 (2005)).